A Sticky Approach to Fighting Infection

BERKELEY, Calif., March 6, 2014 — A new nanoscale approach to studying a common source of infection could ultimately lead to the creation of bacteria-resistant materials as a line of defense.

Scanning electron microscopy reveals how S. aureus cells interact with a nanostructure. A bacterial cell is embedded inside the hollow nanopillar's hole, and several cells cling to the nanopillar's curved walls. Images courtesy of Molecular Cell Biomechanics Laboratory and the Nanomechanics Research Institute.
A team at the Lawrence Berkeley National Laboratory, in collaboration with scientists from the University of Waterloo in Ontario, Canada, has been investigating how individual Staphylococcus aureus cells adhere to metallic nanostructures, and how this could introduce new ways to prevent Staph and potentially other infections.

“By understanding the preferences of bacteria during adhesion, medical implant devices can be fabricated to contain surface features immune to bacteria adhesion, without the requirement of any chemical modifications,” said Mohammad Mofrad, a faculty scientist in Berkeley Lab’s Physical Biosciences Division and a professor of bioengineering and mechanical engineering at the University of California, Berkeley.

The researchers found that bacterial adhesion and survival rates vary depending on the nanostructure’s shape. S. aureus cells can adhere to a wide range of surfaces, from flat, horizontal ones to those that are highly curved. The team hopes to find a surface with properties that make it less inviting to bacteria.

As part of the study, the researchers used electron beam lithographic and electroplating techniques to fabricate nickel nanostructures of different shapes — solid pillars, hollowed-out pillars, C-shaped pillars and X-shaped columns — with outer diameters as small as 220 nm. They also created mushroom-shaped nanostructures with tiny stems and large overhangs.Bacterial cells (shown in blue) are suspended from mushroom-shaped nanostructure overhangs.
S. aureus cells were then introduced to these structures and allowed time to adhere before being rinsed with deionized water to remove all but the most solidly bound bacteria.

Scanning electron microscopy revealed which shapes are the most effective at inhibiting bacterial adhesion.

“The bacteria seem to sense the nanotopography of the surface and form stronger adhesions on specific nanostructures,” said Zeinab Jahed, lead member of the research team and a graduate student.

A higher bacteria survival rate was discovered on the tubular-shaped pillars, where individual cells were partially embedded into the holes; pillars with no holes had the lowest survival rates.

The research was funded by the Natural Sciences and Engineering Research Council of Canada and through a CAREER award from the National Science Foundation. The work is published in Biomaterials.